Field of the Invention
Embodiments of the present invention generally relate to a radio frequency (RF) digital variable capacitor (DVC) units for RF tuning and impedance matching.
Description of the Related Art
MEMS capacitors can show non linear behavior when operated as a capacitor. This is a problem for RF applications when signals transmitted at one frequency can leak into other frequency channels. One measure of this is the IP3 value or the value of input at which the third order nonlinearity times the input voltage or current is equal to the first order term times the input voltage or current.
With a MEMS capacitor, as the power increases on the RF line, an increasing voltage is dropped across the oxide between the RF line and the grounded MEMS cantilever. Even though the MEMS device may be in mechanical contact with the oxide layer, any roughness or asperities at that interface, result in a small change in the gap (between the RF electrode and the grounded MEMS) as a function of applied power. This change in gap results in a change in the maximum capacitance which in turn causes a shift in resonant frequency as a function of power. Thus a modulation in power can then lead to a modulation in frequency and to more signals being found outside the desired frequency window.
Therefore, there is a need in the art for a MEMS DVC with a consistent resonant frequency.